Conventional plasma generators for electrothermal gun cartridges include a pair of axially spaced electrodes between which a capillary extends to generate an electrical arc upon application of an electrical voltage to the electrodes. This electrical arc generates a plasma that ignites a propellant to produce heated and pressurized gas for launching a projectile of the cartridge. Such prior plasma generators are disclosed by U.S. Pat. Nos.: Chryssomallis et al U.S. Pat. No. 4,711,154; Goldstein et al U.S. Pat. No. 4,715,261; Chryssomallis et al U.S. Pat. No. 4,895,062; Goldstein et al U.S. Pat. No. 4,974,487 Goldstein et al U.S. Pat. No. 5,072,647 and Mortensen U.S. Pat. No. 5,444,208.
With such conventional cartridge plasma generators, the electrical arc generated and resultant plasma is not always at the desired location for proper propellant ignition. Furthermore, the relatively large electrical voltage involved of several kilovolts which produces a current on the order of 10 to 100 or so kiloamps produces relatively large electromagnetic and hydrodynamic forces due to the small volumes where plasma is generated. These forces can destroy the cartridge construction and the metallic electrode construction for carrying the current.